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Author Topic: Life as we know it?  (Read 3012 times)

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Offline CWandTopic starter

Life as we know it?
« on: July 05, 2009, 04:18:07 PM »
This occurred to me a long time ago, when i was looking up information on Titan, and various other outer solar system moons.  Do you think that our own bias by earth standards for life, limit the places we look for life?  I mean Chemotrophes can survive in the absence of light entirely.  There are compounds on earth that when heated to certain temperatures will generate light that could support autotrophes.  Couldn't life survive in deep space if it was on a large enough body, such as a dead star's core, or large gas giant that was ejected from its star's influence?  What do you think?

Offline Vekseid

Re: Life as we know it?
« Reply #1 on: July 05, 2009, 04:52:48 PM »
Life can survive in deep space - or many places - but growth in such areas is not particularly likely.

A dead star's core is out of the question, though - no white dwarf is cool enough yet to permit molecular formation at all, and no neutron star surface is going to permit life.

Offline CWandTopic starter

Re: Life as we know it?
« Reply #2 on: July 05, 2009, 05:01:24 PM »
I was actually referring to brown dwarfs and black dwarfs, Vekseid which borderline on being gas giants.  The temperature issue actually isn't as big an issue from what we've seen in Io, and some of the other moons who have molten interiors due to gravitational pull from their planet.  Io, actually has the most active volcanic system in the solar system, its entire surface changing daily due to the tidal forces applied by Jupiter to its surface.   But yes white dwarfs and neutron stars are definitely way to hot for any life to form.

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Re: Life as we know it?
« Reply #3 on: July 05, 2009, 05:06:10 PM »
Dead star's core (which implies that nuclear ignition occurred at one point) is unlikely.  However, it is entirely possible that there are metabolisms that could exist in environments other than the 'Class M' planet.  Look at the colonies of organisms that live near deep-sea thermal vents - extreme pressure, extreme temperature, near complete lack of light.

As such, there could very well be life that Man overlooks purely by virtue of writing off an environment as 'uninhabitable'.

Offline Vekseid

Re: Life as we know it?
« Reply #4 on: July 05, 2009, 05:07:28 PM »
There are no black dwarfs yet - as I mentioned, the Universe is not old enough for them to have sufficiently cooled yet.

Brown dwarfs would be less likely, as they go through a fusion phase that would sterilize any cell that entered them. Possible after that passed, I suppose, but most gas giants are going to be a bit rarefied to support life, as a rule

Offline kylie

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Re: Life as we know it?
« Reply #5 on: July 05, 2009, 06:07:33 PM »

Most of this is rather over my head...  But it got me to thinking, are we more likely to find "life" as we can imagine it (particularly organic matter), or should we expect "signs of life" closer to technology as we know it? 

How comprehensive is the search for things like radio waves?  Can it be reasonably comprehensive, or is the band (or stretch of possible bands) too wide for us to ever search, given all the room out there to explore? 

For that matter...  Is it reasonable to search for electromagnetic stuff to begin with (as a likely product of life that is, setting aside whether it's easier in our own experience to find) - or would looking for object debris be as easy to rationalize?

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Re: Life as we know it?
« Reply #6 on: July 05, 2009, 06:12:41 PM »
Actually, there's a specific band of radio frequencies that is monitored for interstellar activity.  It's the band between the hydrogen line and the strongest hydroxyl spectral line, and is notable for being a quiet region between two notable frequencies.

http://en.wikipedia.org/wiki/Water_Hole

Offline CWandTopic starter

Re: Life as we know it?
« Reply #7 on: July 05, 2009, 06:15:15 PM »
SETI (search for Extraterrestrial Intelligence) maintains several hundred radio telescopes looking for radio waves. however from what i understand, radio waves break down into garble beyond a few light years so its not really that useful to search in this manner. But your right the range signals could be in is far greater then we realize considering how light works.  Wavelength, by definition gives an infinite number of possible wavelengths, frequencies and amplitudes, realistically we can't search them all and due to the Doppler effect we can't conceivably receive on them all either.  Also there's ALOT of background radiation that interferes with numerous wavelengths.

Oniya is right however that there are established frequencies we check.

Offline Paradox

Re: Life as we know it?
« Reply #8 on: July 05, 2009, 06:18:55 PM »
Life is possible in all kinds of places, but as Veks hinted at earlier-- complex life is much more limited. The conditions required for the development of the building blocks of life into more complex organisms are-- as far as we can tell so far-- fairly limited in range.

I remember Midnight At The Well of Souls and The Andromeda Strain, where there were creatures based entirely on crystals, but non-carbon-based lifeforms notwithstanding, we should be looking for a relatively Earth-like planet.

Offline CWandTopic starter

Re: Life as we know it?
« Reply #9 on: July 05, 2009, 06:21:49 PM »
I'd have to disagree Paradox given that chemotrophes can survive in complete darkness.  There are complex organisms that can survive in blow freezing temperatures all their lives by secreting antifreeze like compounds into their blood, and there are even creatures that can survive at boiling temperatures near volcanic vents.  The range in which life can survive is widen then what we thought.

Offline Paradox

Re: Life as we know it?
« Reply #10 on: July 05, 2009, 06:25:06 PM »
CWand- I'm well aware of chemotrophs, halotrophs, and all sorts of other extremophiles. Notice the italicized word in my previous post.

complex life

The creatures that live in such extreme conditions are indeed lifeforms by our definition, but they're pretty damned primitive. That's my point. You don't see any mammal swimming around volcanic vents, and "complete darkness" isn't really "extreme". We have blind bats using echolocation every day.

Offline CWandTopic starter

Re: Life as we know it?
« Reply #11 on: July 05, 2009, 06:29:06 PM »
you see salamanders, insects, and an assortment of what i consider complex life.  That live in complete darkness in subterranean caves that are completely closed off from the surface, fungi and bacteria being the only source of autotrophes available to them for a steady income of energy..  The vents your right on, the extreme colds of the arctic ocean hold hundreds of species of fish, squid, and crabs that have evolved to live in below freezing temperatures.  I suppose it comes down to what is considered complex life there though.

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Re: Life as we know it?
« Reply #12 on: July 05, 2009, 06:30:03 PM »
The question is, what if there was an environment where such creatures had fewer limitations on food and space (which is one thing that limits their evolution here on Earth)?  And what if they came into being a couple million years earlier than we did, and therefore had longer to evolve?

Offline The Overlord

Re: Life as we know it?
« Reply #13 on: July 05, 2009, 06:33:34 PM »
There are no black dwarfs yet - as I mentioned, the Universe is not old enough for them to have sufficiently cooled yet.


Of course if there were any yet, could we even find them, outside of getting lucky and being able to detect their mass.

Offline CWandTopic starter

Re: Life as we know it?
« Reply #14 on: July 05, 2009, 06:37:27 PM »
Overlord that's actually part of the Nemesis debate from what little i understand about it.  Not that i put much stock in Nemesis.  The theory states that the Solar system is actually a binary system, with a black or very dim brown dwarf as its partner.  Its meant to explain the consistent mass extinctions caused by asteroid/comet impacts and a void of debris found in the Orde (sp?) cloud on the fringes of our solar system.

Offline Vekseid

Re: Life as we know it?
« Reply #15 on: July 05, 2009, 06:55:34 PM »
you see salamanders, insects, and an assortment of what i consider complex life.  That live in complete darkness in subterranean caves that are completely closed off from the surface, fungi and bacteria being the only source of autotrophes available to them for a steady income of energy..  The vents your right on, the extreme colds of the arctic ocean hold hundreds of species of fish, squid, and crabs that have evolved to live in below freezing temperatures.  I suppose it comes down to what is considered complex life there though.

All multicellular organisms on Earth rely on the oxygen cycle.

Offline CWandTopic starter

Re: Life as we know it?
« Reply #16 on: July 05, 2009, 07:03:02 PM »
Mostly true we can use the *tries to remember the proper term* Lactic acid? Cycle, but we do prefer the kreb cycle over it due to efficiency reasons. namely for the Lactic acid cycle you get 2 ATP for every molecule of sugar consumed, whereas with the Kreb cycle i believe its 32? 36? somewhere in there.  When your legs burn after exercise that's because they've shifted over to the lactic acid cycle to make up for dwindling oxygen supplies in the blood.  Its not as effective and limits the size of organisms considerably but it does work.  The main drawback being that with only a few exceptions H Pylorea for example, no organism can function in a Ph lower then 4 or so.  H Pylorea is a bacteria that causes stomach ulcers in humans, it can survive in Ph 1 due to its unique ability to secrete bases into its environment.   Other methods likely exist for the extraction of energy from sugar though, that we don't know about because they never evolved and became as popular as our Kreb cycle.

Offline The Overlord

Re: Life as we know it?
« Reply #17 on: July 05, 2009, 07:18:38 PM »
Overlord that's actually part of the Nemesis debate from what little i understand about it.  Not that i put much stock in Nemesis.  The theory states that the Solar system is actually a binary system, with a black or very dim brown dwarf as its partner.  Its meant to explain the consistent mass extinctions caused by asteroid/comet impacts and a void of debris found in the Orde (sp?) cloud on the fringes of our solar system.

The Nemesis theory is based on a brown dwarf, or a star that’s so low-mass and low-emission that we’ve yet to detect it, or so the theory goes. As it nears us it disturbs the Oort cloud, sending cometary nuclei hurtling sunward.


Based on what I’ve read to date, the major global extinctions are most likely the result of galactic migration. As the solar system revolves about the core of the galaxy every quarter-billion years, it also bobs up and down out of the plane of the galactic disc, almost like a boat riding waves, and I’d be curious if the fluid dynamics of the interstellar medium are doing just that to us.

Current knowledge indicates the mass exhibitions are congruous with the points where the solar systems passes through the dense main plane of the galaxy; the point when the amount of interstellar material surrounding us is at a high, thus serving the same function postulated the existence of Nemesis.

Offline Mnemaxa

Re: Life as we know it?
« Reply #18 on: July 05, 2009, 08:15:02 PM »
The thing that truly limits where we look for life are the capabilities for us to look for it. 

Despite recent events, our ability to explore the universe is limited by how we can perceive things as a species, as well as how our equipment can perceive things.  Our equipment is sophisticated enough to perceive a much, much broader range of phenomena than we ourselves can, and can translate it into things we as humans can process as data, but the truth of the matter is even that sophisticated equipment is missing incredibly large sections of the phenomena of the universe - and that's phenomena we KNOW about.  The amount of phenomena that we DON'T know about and understand is still vast, and every few days we learn something new about the universe as a whole even with out severely limited perceptions.  Humanocentrism aside, we are very limited in terms of sensory capacity, even in comparison to the animals and plants we share the world with.

Space exploration is costly, and difficult, and fraught with problems.  We have made achievements, and we are getting better - and faster - at it, by by and large we have to trust in equipment that can barely function on the simplistic programs we set up for it.  And that equipment is beyond our reach, most of the time.  Still, we are making progress, slowly and surely. 

My personal opinion is that when we do discover life in the universe, it will be much stranger than we anticipated it would be.

Offline kylie

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Re: Life as we know it?
« Reply #19 on: July 05, 2009, 08:43:43 PM »
Quote from: Mnemaxa
Despite recent events, our ability to explore the universe is limited by how we can perceive things as a species, as well as how our equipment can perceive things.  Our equipment is sophisticated enough to perceive a much, much broader range of phenomena than we ourselves can, and can translate it into things we as humans can process as data, but the truth of the matter is even that sophisticated equipment is missing incredibly large sections of the phenomena of the universe - and that's phenomena we KNOW about...

This feels closer somehow to the part that grabs me.  Not being educated on much of the heavy astronomy or chemistry, I won't weigh in on "what life might be."  I'm trying to guess in general terms of techniques of searching versus the range of comprehensible "signs" out there. 

Much as we're already searching for radio waves, are we actually searching for say, other searching machines not of our making? 

Are we more likely to find life forms, or their technical products?  Perhaps we can't imagine every possible means of space travel, but it sounds to me like so much of the discussion revolves around the ordering of "life."  Isn't it easier to find stuff that can travel around, or stuff that has been crafted, than it is to find life as we know it?  Even if the products we can identify were possibly out of date or left behind.
   


Offline The Overlord

Re: Life as we know it?
« Reply #20 on: July 05, 2009, 08:58:19 PM »

The question has been raised by xenobiologists before, if we do discover extraterrestrial life, will we know it when we see it?


Our solar system makes a tremendous model for what to expect of the galaxy, but not in the way we once thought. Once upon a time, and not so long ago, we thought our star system was a nice tidy little place. Four terrestrial worlds near the sun comprised of metals and silicates, four gas giants further out made mostly of hydrogen, helium, water and methane, etc.; nicely partitioned by an asteroid belt. Of course there was that odd man out, Pluto, but no biggie. Perhaps it was a fluke of creation.

The gas giants had many moons we learned, and once we started counting them we found more and more. We expected them to be largely dead, cratered and uninteresting places like our own Moon. Of course this is before we suspected the Moon had water deposits…


Missions like Pioneer, Voyager, Galileo and Cassini changed all that forever. No two moons are the same, and have widely different appearances, compositions, and geologic histories. On at least one there is active volcanism, and on others cryovolcanism. There are suspected subterranean oceans on the large moons orbiting Jupiter, and mysterious geyser vents on the outer edge of the solar system orbiting Neptune. Then there's Titan...

We now know Pluto was but the first of thousands of KBO’s, Kuiper Belt Objects, perhaps millions. Enigmatic places emerged from the blackness. Eris, Makemake, Haumea, Sedna, Orcus, Quaoar, and Vuruna…places that seemed more out of a science-fiction novel than real worlds, however far and remote.


And all this, orbiting one stable, type-G sub-dwarf star that is not particularly interesting or uncommon, given the spectrum of stellar objects we find out there, pun intended. My point should be obvious; all this in one little star system, and we know of at least 300 planets around nearby system, and counting. Most of these planetary models do not even remotely resemble the standard model we thought ours represented. Hot Jupiters, Super-Earths, 2nd and 3rd generation planets? Oh my, the galaxy is turning out to be a rather interesting place.


I sincerely believe our imagination is not up to the task. We should impose only the most realistic boundaries and restrictions on where we might find life, and then prepare to be massively surprised. The universe has been known to throw us more than a few curve balls.

Offline Serephino

Re: Life as we know it?
« Reply #21 on: July 05, 2009, 09:57:07 PM »
You know, I've often wondered the same thing.  No one knows exactly how life came to exist on Earth, but it did.  And life evolved using what was available.  Living organisms on this planet need water and oxygen to survive, and there's enough of it here for that work.  But I've always thought it was a little closed minded to assume that life could not possibly exist without those things.  If we've learned nothing else from exploring extreme environments on our own planet, we've learned life can and will find a way.  Like you were saying earlier, there are living organisms near volcanic vents and at the bottom of arctic oceans in temperatures that were once thought to be incompatible with life.  Who's to say that life couldn't evolve using other elements and compounds?  Who's to say there aren't compounds out there that are better for creating life than water that we just haven't discovered yet?

Offline Mnemaxa

Re: Life as we know it?
« Reply #22 on: July 05, 2009, 10:10:31 PM »
People do tend to forget that hemoglobin is one of SEVERAL types of methods for moving oxygen through the bloodstream, even here on earth. 

Copper sulfate and magnesium sulfate are commonly used in arthropods; bacteria and other one-celled organisms that don't even have circulatory systems are not dependent on such things at all, which means it is entirely possible that the system could be bypassed in favor of other methods. 

There was life on earth before we started breathing one of the most corrosive substances on the planet, after all....and chlorophyll is not the only photosynthetic substance either - plum trees don't use it, after all. 

Even on earth the 'facts of life' are not entirely linear....

Offline CWandTopic starter

Re: Life as we know it?
« Reply #23 on: July 05, 2009, 10:13:00 PM »
Life as we know it actually only needs two things. Amino acids, water and De-oxyribonucleic acid. in fact to some life oxygen is a deadly poison that kills it instantly. Just ask N. Gonera :P that stuffs impossible to grow in a oxygen rich environment such as our own.  You have to put it in a CO2 rich incubator for at least twenty four hours to get ANY growth at all.

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Re: Life as we know it?
« Reply #24 on: July 05, 2009, 10:32:09 PM »
Copper sulfate and magnesium sulfate are commonly used in arthropods;

One of the oldest life forms still existing - the horseshoe crab - has a copper-based blood.